1. Field of the Invention
The present invention relates to antennae used in wireless communication that are mounted in electronic devices, adjustment methods for such antennae, and electronic devices in which such antennae are mounted.
2. Description of the Related Art
In recent years, electronic devices such as personal computers that include wireless communication functionality, as represented by wireless LAN, Bluetooth®, and so on, have been spreading. Wireless communication over wireless LAN, Bluetooth®, and so on is carried out using radio waves in, for example, the 2.5 GHz band, the 5 GHz band, or the like.
A personal computer provided with such wireless communication functionality includes an antenna for wireless communication; various types of antennae are used depending on the model of the computer, such as a dipole antenna, a helical antenna, a slot antenna, an inverted-F antenna, and so on.
Due to reductions in the sizes of electronic devices, these various types of antennae are being required to be mounted in areas that have limited mounting space, and there is also a demand to reduce the costs thereof. To put this differently, attempts are being made to reduce costs by mounting antennae as patterned forms upon the boards of wireless module chips, rather than mounting the antennae separately.
However, in the case where an antenna is mounted in an electronic device such as a PC, there is a problem in that the frequency characteristics of the antenna change depending on the components that are located in the periphery of the antenna, resulting in the frequency characteristics obtained when the antenna is mounted differing from the frequency characteristics obtained when the antenna is in a standalone state.
Thus far, changes in the frequency characteristics of an antenna occurring due to the antenna being mounted in an electronic device are absorbed by the antenna. For example, desired frequency characteristics are achieved for an antenna when the antenna is mounted by using various methods, such as adjusting the shape of the antenna. The following can be given as examples of documents that disclose absorbing, through the antenna, changes in antenna characteristics caused by the surrounding environment of the antenna.
(1) The length of the short stub portion in a radiating element that functions as a cavity resonator is adjusted by changing the location of a through-hole, which adjusts the resonating frequency. The adjustment of the resonating frequency is carried out by changing the length of the stub that configures part of the radiating element (for example, U.S. Pat. No. 5,483,249).
(2) Multiple stubs having free ends are formed connected to a microstrip line-type resonator in advance, and are shorted through soldering in a state where opening patterns are formed in the vicinities of the free ends of the stubs; the resonating frequency is then adjusted by changing the capacities of the stubs connected to the resonator. The adjustment of the resonating frequency is carried out by changing the lengths of the stubs that configure part of a radiating element (for example, Japanese Patent Laid-Open No. 09-162642).
However, there is the following problem with the stated past methods of bringing a change in the frequency characteristics of an antenna, occurring when the antenna is mounted, in line with desired characteristics by adjusting the shape of the antenna. That is, because the environment in which the antenna is mounted differs depending on the type of electronic device, the change in frequency characteristics occurring when the antenna is mounted is not always the same, and thus the same antenna cannot be used in different types of electronic devices.